I try to be sure my tegus and my monitor do NOT get obese. They are fed either every other day(light meals of 1 mouse) or every third day(2-3 mice), and I go heavy on fruit(mainly apples and grapes) in between.
If you look at other than the belly, Noah is not particularly fat elsewhere, AND today Noah decided to make a nest like den(in the rubbermaid den I put in) in the pen. Perhaps she is prego. We'll have to see. I feed by tongs, so I know Noah is not eating everyone's food too(mice, obviously, not the fruit).